This invention relates to methods by which a predispostion to premature ovarian failure can be detected as well as to methods of diagnosis of premature ovarian failure. Still further, this invention relates to methods of therapy.
Premature ovarian failure (POF) is a condition causing secondary amenorrhea, hypoestrogenism, and elevated gonadotrophins in women younger than 40 years. POF will occur in 1% of women before the age of 40 years and in 0.1% or 1 in 1000 women before the age of 30 years (Coulam, Adamson et al. 1986). POF can be familial, genetically inherited, or sporadic where there has been no family history of the disorder. Even though there have been many advances into the cause of POF in the last few years, especially in the field of molecular genetics, the cause of POF in most cases remains a mystery. Most women presented with idiopathic POF have normal menstrual history, age of menarche, and fertility prior to the onset of the condition. It was once thought that POF was irreversible in all cases as in menopause, however, intermittent ovarian failure has been reported, and pregnancy can occur in approximately 10% of patients subsequent to diagnosis.
The most immediate concern for women with POF is the menopausal symptoms they experience due to the decrease in circulating oestradiol coupled with the psychological implications of these symptoms. The menopausal symptoms include hot flushes, night sweats, insomnia, palpitations, headaches, incontinence, and dyspareunia as a result of vaginal dryness. The psychological implication of POF not only include those associated with menopause such as forgetfulness, poor concentration, irritability and mood swings.
A second consequence of POF is the loss of fertility. Even though some women will spontaneously ovulate and achieve a natural pregnancy most women with POF will not. Infertility treatment is difficult, as in many cases the ovary does not have any follicles left. In the cases where follicles can be detected by biopsy, the ovary has become unresponsive to FSH. Therefore, most women with POF can either choose to adopt children or undergo donor egg IVF. However, obtaining donor eggs can be difficult and the procedure can be very expensive.
The longterm consequences of POF are caused by the increased length of time the body will be without ovarian oestrogen. The risk of osteoporosis and cardiovascular diseases increases after menopause due to a decrease in oestrogen that appears to provide a protective effect against these diseases. Women with POF have reduced oestrogen levels for between 20 to 30 years longer than normal women. Therefore, the risk of these diseases is thought to be much greater in women with POF. For this reason patients with POF are prescribed hormone replacement therapy (HRT). However, these women have an additional concern. The prolonged use of HRT has been associated with an increase in the risk of acqguing breast cancer, endometrial cancer and gallstones. Until research into the long-term effects of HRT in women with POF have been conducted this issue will still be a major concern for these women.
The identification of genes predisposing to POF is therefore an essential step towards understanding the molecular events underlying this condition. It is also critical for clinical management of affected individuals and POF therapy.
Most women with POF are found to have follicles, but they do not appear to respond to normal gonadotrophin stimulation. However, very few mutations have been identified in gonadotrophin hormones or their receptors. The loss of function mutation, 566C greater than T, identified in the FSH receptor (Aittomaki et al, (1995)) was found to cause ovarian failure with primary amenorrhoea in a group of Finnish families. It appears that this FSH receptor mutation is rare elsewhere, as it has not been detected in other populations (Conway (1997), Layman et al (1998)). Ovarian resistance has also been seen in association with a premature stop codon in the luteinising hormone receptor gene (Latronico et al (1996)). However, while these data demonstrate the obvious importance of the FSH axis in ovarian function, they do not identify which molecular events are causative of POF.
The applicants have now identified a gene in individuals which, when mutated, appears associated with a predisposition on the part of that individual towards POF. It is this finding, and the implications it has for POF screening and management (particularly for individuals with a family history of POF) which underlies the present invention.
Accordingly, in a first aspect, the invention broadly provides a method of testing to detect whether an individual has, or is predisposed to, POF which comprises the step of detecting the presence or absence of an alteration (mutation) in the gene encoding inhibit.
As used herein, the term xe2x80x9cgene encoding inhibinxe2x80x9d means INHxcex1, INHxcex2A, and INHxcex2B, together with their non-coding fanling sequences and regulatory elements.
In one (preferred) embodiment, the presence or absence of the mutation is detected through analysis of the DNA encoding inhibin and/or its regulatory elements.
In an alternative embodiment, the presence or absence of the mutation is detected through analysis of mRNA transcribed from the DNA encoding inhibin.
In still a further embodiment, the presence or absence of the mutation is detected through analysis of the amino acid sequence of the expressed inhibin protein.
As a separate embodiment, the invention provides a method of prophylaxis and/or therapeutic treatment against POF of an individual identified as having a risk of POF by a method defined above or suspected to have such a risk which comprises the step of increasing, maintaining and/or restoring the active concentration of wild-type inhibin protein within said individual.
Conveniently, the method will be a gene therapy method and will involve supplying the individual with wild-type inhibin gene function.
Most preferably, the method will involve administering wild-type inhibin to the individual.
In still a further aspect, the invention provides for the use of inhibin in the manufacture of a medicament for treating or preventing POF.